Added net9.0 to the TargetFrameworks

Author: kubagdynia

.github/workflows/dotnet.yml

@@ -35,6 +35,11 @@ jobs:
       with:
         dotnet-version: 8.0.x
 
+    - name: Setup .NET 9.0.x
+      uses: actions/setup-dotnet@v4
+      with:
+        dotnet-version: 9.0.x
+    
     - name: List installed .NET SDKs
       run: dotnet --list-sdks